Spherical rotary compressor



Dec. M, 1952 P. PISA SPHERIOAL ROTARY COMPRESSOR Filed Jan. 6, 1949 ICA/VBN Tol? n www A fo @Ney ec., i6, 1952 P. PlsA 2,621,852

SPHERICAL ROTARY COMPRESSOR Filed Jan'. 6' 1949 4 sheets-sheet 2 P I XTM-X1 f5 O l O 1j O O 7 O 2 O Z A O o s vf: O

GTTONEY Dec, l, 11952 Filed Jan. 6. 1949 P. PISA '2,621,852

SPHERIOAL ROTARY COMPRESSOR 4 Sheets-Sheet 5 7i@ @ab INVENT'QR .Dea 69 1952 l P, P|5A 2,621,852

SPHERICAL ROTARY COMPESSOR Filed Jan. 5. 1949 4 Sheets-Sheet 4 Patented Dec. 16, 1952 2,621,852 y srHERicAL ROTARY COMPRESSOR Pietro Pisa, Rome, Italy Application January 6, 1949, Serial No.V 69,53

' In Italy February 2, 1948 s claims. (c1. 23o-131 )f Subject matter of the present invention is a rotary compressor, with a spherical Work chamber, said compressor being of the volumetric type having high output and minimum bulk. The compressor is adapted to run at high speed and is capable of operating from the low to the medium pressures.

The work chamber of the compressor is termed spherical inasmuch as the chambers wherein both the suction and the compression take place are partially limited by spherically shaped walls.

It is an object of this invention to provide a rotary compressor with a spherical housing in which the suction and compression chambers are formed by two pairs of vanes, in cooperation with a housing having an inner spherical surface, said chambers passing from a minimum to a maximum volume and vice versa by means of an oscillatory motion of the vanes, perpendicular to their rotating motion, caused by two guides, substantially conical, xed to the housing whereon said vanes bear during their rotation.

It is another object of the invention to provide guides for the vanes having a surface substantially frusto-conical permitting the constant contact of the vanes with the guides by means of rollers, during the rotation of the said vanes.

It is a further object of the invention to provide a rotary compressor, having a large volume of sucked air in one turn of the machine andwherein it is possible to reach rather high compression, the rotating part being controlled by compact and fast members having a rolling motion. With this and other objects in view, as willappear fromfthe following description and drawings, the invention consists in the novel features of construction, combination of elements and arrangement of parts hereinafter fully described and pointed out in the appended claims.

In the enclosed drawings is illustrated by way cf example an embodiment of the machine of the industrial type.

Figure 1 illustrates the cross sectional View of the Figures 2 and 3 taken on the line I-l Figure 2 is a longitudinal section of the Figures 1 and 3 taken on the line II-II.

Figure 3 is a cross sectional view of the Figures 1 and 2 taken on the line III-III.

Figure 4 shows a detail of the compressor, being a section on the line IV-IV in Fig. 5.

Figure 5 shows a section taken on the line V-V of the Figure 4, and

Figure 6 shows a section taken on the line VI-VI of the Figure 4.

Figure 7 illustrates a view of the vanes roi" vthe compressor.

Figure 8 is a section taken on the line VIII- VIII of Figure '7.

Figure 9 shows a perspective view of the geometrical conditions to be operated by an element of the compressor.

Figures 10 and ll are two cross Sectional Views taken on the lines X--X and XI-Xl of the Figure 2 of elements of the compressor with the housing removed. A

The compressor shown by way of example in the drawing comprises a housing having a frustospherical inner surface formed by two shells l and two opposite end walls 23. A shaft -I, journalled at its ends in conicalbearings in the end walls 23 and connected by coupling means with a motor, is provided in its median portion with an enlargement 2 of square cross-section (Figs. l

and 2). v v

Normal to the axis of the shaft l and fixedto the shaft at its midpoint is a large cylindrical pivot 3 (Fig. 2) which rotates with the shaft ina plane perpendicular to its axis. At its opposite ends the pivot has enlarged heads I2 with spherical outer surfaces conforming' in curvature to the inner spherical surface of the housing. A

Two pairs of vanes 4 are mounted on the pivot 3. Each ofV the vanes 4 has the general shape of a segment of a. circle, being shown approximately semi-circular. The two` vanes of each pair are joined with one another along their straight or inner edges by a hub portion so that the vanes form a .wide-open V relative to one another. The hub lportions of thev two pairs Vare coaxial with one'another and both are oscillatably supported on the pivot 3 in somewhat the same manner as two wings of a hinge on a hinge pin. The two pairs of vanes are thereby adapted to rotate with the shaft l about the axis of the shaft and to oscillate about the axis of the pivot 3 so that the facing vanes ofopposite pairs alternately ap.- proach and recede from one another.

The segmental vanes 4 have arcuate peripheral rim-or border portions which have a radius substantially equal to that of the spherical inner surface of the housing and are adapted to slidablyl engage said inner surface, it being undertstood that there may be lubricant or other sealing means between the surfaces so that the rims of the vanes do not actually touch the inner surface of the housing. As the shaft l rotates, the vanes 4 have a two-fold motion: a rotary one due to their being dragged along by the actuating shaft I, and an Yoscillatory one about their pivot 3 '(Figures 1 and 3).

lThe -semicircular borders'of these vanes, in all rcombinations of their motions, describe'always spherical surfaces the centres of which are the crossing-point of the axis of the shaft I with that of the pivot 3, this being the centre of the system.

The vanes are contained in a housing (Figures l, 2 and 3), the inner spherical surface of which cooperates with the said vanes to form two chambers for the suction and compression of the air.

By eifecting during the rotation of the shaft I an oscillatory motion of the vanes (-a complete oscillation for each revolution) each of these two chambers will pass from a maximum volume to a minimum one, and from a minimum volume to a maximum one.

Within one chamber, during the half of a revolution, there will be a suctionI whereas during the successive half-revolution a compression will take place therein; hence, two suctions and two compressions for each revolution of the shaft.

The alternating and oscillatory motion of the vanes on the pivot during its rotation in the plane normal to the axis of the shaft I is deter mined through the rolling of the rollers 5 along a continuous guide B fixed in its position in the housing (Figures 1 and 3).

The rollers 5, two of them for each pair of vanes, are fast therewith and arranged diametrally with their axes in the medium plane normal to the tw-o semicircles.

The surfaces of the guides 6 are su-bstantially frusto-conical and the ideal vertex of the cone is in the center of the system and the generatrix of contact with the rollers 5 is always parallel to the rotating axes of the rollers.

Base planes of two sliding guides 6 (projections b-b, Figure 1) have the same inclination in respect of the shaft I; hence they will approach each other in the top portion of the compressor and recede from each other in the bottom portion thereof.

By the rotation of the shaft I the pivot 3 normal thereto drags in rotation the two pairs of vanes 4, which, actuated by the aid of the rollers 5 always in contact on the two guides 6 equally inclined between them, are caused first to recede from, and then to approach, one another.

The inlet of the air into the compressor is effected through the funnel 8 and the opening 9 (Figures 2 and 3). The outlet is on the opposite side through the opening I0 and the conduit II.

The two openings are symmetrical in respect to the plane of rotation of the pivot 3. These openings have a diameter smaller than that or the head I2 of the pivot, and are hence closed thereby as shown in Figure 2.

The air-suction starts when the pivot 3 by one of its big spherical heads I2 has uncovered the opening 9.

In such position the upper vanes 4 are somewhat apart. They have created a depression, and the air through the opening 9 penetrates into the interior of the chamber limited thereby.

The vanes 4 (Figures l and 2) continue Iopening until they have reached, after a half revolution, the position corresponding to the lower maximum opening, wherein suction is left off since the opening 9 has been closed by the head I2.

At the end of the suction, in order to ensure air flow, even when the heads I2 close the opening 9, in the centre of each head I2 there is a terminal bore connected with a small elbowshaped passage I3, provided in the interior of the head, for the purpose of ensuring communication between the -outside and the suctionchamber.

Near the end of suction, owing to the inertia of the air motion, there is the possibility of having a certain amount of air flow into the chamber through the passage I3, during the decrease of volume in the chamber, compressing the air and hence obtaining a higher volumetric output.

During the other half revolution, the two opposite vanes 4 begin to approach each other so that there is no further communication with the outside and the air compression is initiated. (The chamber initiating the compression is the lower one--Figure 1.)

Over the outlet opening I3 (Figures 2 and 3) which has a diameter by far smaller than that of the heads I2, a self-acting check valve I4 opens outwardly. This valve is located inside the conduit II which conveys the air into a reservoir (not shown).

The valve I4 opens only when the pressure of the air overcomes the action of the spring and of the air pressure in the conduit.

The limits of pressure within which such compressor is operated are very wide. The lower limit is determined almost totally by the resistance of the spring of the valve, whereas the upper one is determined by the mechanical strength of the driving elements, the inclination of the guides 5 (providing that the motors power be the same) and, lastly, the efciency of the airtight sealing. Such limits may vary from 1.5 to 8 atmospheres.

The compression is continued until the vanes are in their closest position, in respect to each other; such a distance might be comparatively small (upper position of the vanes, Figure 1), thus reducing the waste space to its minimum value.

Before reaching such a limit of position, after the closure of the outlet opening by the head I2, the air continues to flow out of the com-pression chamber through the said elbow-shaped passage I3.

The grooves I5, provided at the base of each vane 4 (Figures l, 2 and 3) when the vanes are closed, constitute a canal for the conveyance of the compressed air remaining in the elbow I3, in communication with the self acting valve I4.

In this compressor, like piston compressors, the ow of air is of a pulsating nature; thus requiring an equalizing reservoir, the volume of which is still smaller, at identical output, owing to the fact that there are two compression strokes for each revolution, instead of a single compression stroke, as is the case in piston compressors.

The rollers 5 are compelled to press without interruption, against the sliding guides 6, due to the action exerted by small leaf springs I6 located in the cavity I'I provided in the wall of the Vvane 4, in which the base of the oscillating arm I8 which is bearing the roller 5 (Figures 1, 3, l1, 5 and 6) penetrates.

The arms I8 oscillate about pivots I8 parallel with the axis of rotation of the rollers 5, and set diametrically opposite each couple of vanes (Figures 4, 5 and 6).

The axes of the pivots I9 are therefore parallel with the generatrices of contact of the rollers with the sliding guides 6. During the oscillation the roller is always parallel to the first conical surface of the guide 6.

In order to compensate for the small differences in the sliding motion, the external surfaces of the rollers 5 are slightly convex (Figures 1, 3, 4, 5 and 6).

The leaf-springs I6 besides maintaining the continuous contact between the rollers and the guides, serve also to damp the knocking which takes place when the direction of the oscillatory motion of vanes ll changes.

Also the compressed air tends to damp the said knockings, inasmuch as it causes the guides to continuously follow the couples of rollers opposite to those which cause the vanes to invert the sense of their oscillations.

The airtight sealing is obtained through the extended surfaces of the borders of the vanes set in contact with the spherical walls of the housing, the lubricating oil being suicient to obtain a satisfactory sealing against air leakages.

Such airtight sealing in between the two couples of vanes is obtained by means of the large cylindrical sliding surfaces of the pivoting hubs (Figures 7, 8, 10 and 11).

When the compressor is working in the high pressure stage, it is necessary for the vanes to be provided with a plurality of elastic sealing segments 20 wedged along the semicircular borders thereof and arranged in the shaps of a maximum circle of the sphere (Figures '7 and 8). The said sealing segments are put under stress by having their extremities wedged inside the appropriate lodgings provided in the walls of the vanes themselves, and having their ends in contact with the cylindrical surface of the heads l2. The heads l2 are further provided with a ring 2| located at the end thereof, in contact with the spherical walls f the housing and located inside the spherical surface of the head (Figures 7 and 8).

This ring having an outer diameter equal to that of the head, is pushed by centrifugal force so that it presses against the spherical walls, in order to ensure the airtight sealing along the circular border of the head.

The heads I2 are held in place by screws 22 which also adjust the play lbetween the heads and the housing (Figure 2).

The two shells 1 of the housing are supported by the end walls 23 which also contain the rollerbearings serving to support the driving shaft l (Figures 1 and 3).

A plate 24 serves as a common base for the two end walls 23.

When the rollers are in the position shown in Fig. 1, the angle a of the ideal cone formed by the contact generatrices of said rollers is equal to the angle ofthe ideal cone formed by the guides 6, as the plane of the drawing of Fig. 1 contains the height h common to the two ideal cones.

Due to the fact that the projection b-b of the basic circles of the said two cones are convergent in respect to the pivot 3, when the vanes 4 take the position shown in Fig. 3, the two cones which rst were tangent are now no longer tangent, and namely the ideal cone formed by the guide surfaces 6 will have a vertex angle which is smaller than the angle a of the ideal cone formed by the rollers 5, which angle a remains unvaried.

Consequently, in the position shown in Fig. 3, contact would not be maintained between the rollers 5 and the guides 6. In order that this contact remain constant, independently of the action which may be exerted by the leaf springs I6, the thickness of the guides 6 is increased, as the cross-hatching indicates in Fig. 3.

For this reason the surfaces of guides 6 are not completely frusto-conical, but only substantially frusto-conical. In order to balance the 6 rotating masses, the two vanes of each couple are equal and of the same weight; similarly, the rollers 5 are equal too.

The cooling of the compressor, useful in the case of pressure-ranges over 3-4 atmospheres, is secured by radiation. On the outside surface of the shells 1 in the top-portion serving for the compression, there are small wings 25 embodied therein during the casting of the shells (Figure 2).

The openings 28 (Figure 1) in the end walls 23 allow the air-circulation inside the compressor, a circulation which is continuously activated through the very motion of the vanes.

The lubrication of this type of machine is ensured by both gravitational and centrifugal forces.

The oil contained inside the tank 21 penetrates by gravity into the passage 28 provided along the axis of the shaft I.

From the small radial holes 29 which are alternately uncovered by the vanes, the oil, by virtue of the centrifugal force, is hurled against the rollers 5 and the spherical walls of the shells 1.

Through the other radially set small holes 30, the oil lubricates the supporting roller bearings, and by the passages 3| (Figure l) it flows downwardly to lubricate, running through the small apertures 32, and the walls of the guides 6 in contact with the rollers 5.

The pivoting eyelets of the vanes A, on pivots 3, are lubricated lby the system of small canals 33 (Figure 2) provided inside the pivot 3.

The circulation is provided by the centrifugal force, in this case.

In this type of lubricating both the inlet and outlet holes of the various small canals should be gauged in such a way as to not provoke the rapid exhaustion of the oil in the tank 27. To counteract the action of the centrifugal force acting upon the rollers 5 and upon their arms I8 owing to the rotary motion of the vanes 4 to which they are attached by means of the pivot I9, there will be inserted between the walls of the arm i8 and that of the small cavity I7 (Figures 4, 5 and 6) a small plate 34, applied on to the vane 4, the surface of which serves for the very short sliding movement of both the arm I8 and the respective rollers 5, which thus become relieved from the centrifugal force.

I claim:

1. A rotary compressor comprising in combination a housing having a frusto-spherical inner surface and two opposite end walls, a driving shaft rotatably supported by said end walls, a pivot xed to said driving shaft at its midpoint, said pivot being perpendicular to the shaft and rotating therewith, two pairs of vanes, each vane having the shape of a segment of a circle, each pair consisting of two vanes fixed relative to one another in a wide-open V shape and a hub portion joining said vanes at their straight sides, said vanes having arcuate peripheral rim p0rtions slidably engaging the inner spherical surface of the housing and said hub portions being coaxial with one another and both oscillatably supported on said pivot, said pairs of vanes being thereby adapted to rotate with said shaft about the axis of the shaft and to oscillate about the axis of said pivot, and a guide for each of said pairs of vanes, said guides being provided on the inside of the housing adjacent the end walls and having substantially frusto-conical guiding surfaces, the projected vertices of said frusto-conical surfaces coinciding at the intersection of the axis of said pivot and the axis of said shaft and Ithe axes of said frusto-conical surfaces being disposed at approximately equal angles to the axis of said shaft and being disposed relative to one another in a wide V, the angle of which is approximately equal to the angle between two vanes of a pair, said two pairs of vanes being adapted, during their rotation, to follow said guides in such manner as to cause each vane of one of said pairs to move alternately toward and away from the facing vane of the other pair so as to form in cooperation with the spherical surface of the housing a suction chamber when ,the two facing vanes move away from one another and a compression chamber when the two facing vanes move toward each other, and inlet and outlet openings for said chambers.

2. A rotary compressor according to claim 1 having rollers on said vanes by means of which rollers said vanes are caused to follow said guides, the axes of rotation of said rollers being constantly parallel to the surfaces of said guides, an oscillating arm connecting the rollers to the vanes, and springs for maintaining contact between the rollers and guides.

3. A rotary compressor according to claim 2, wherein the said frusto-conical guides have a gradual variation of thickness to compensate for deviation of said rollers from a true conical path and thereby maintain contact between the said guides and the rollers.

4. A rotary compressor according to claim 1, wherein elastic sealing elements are wedged into recesses in the arcuate peripheral rim portions of said vanes and engage the inner spherical sur face of the housing to provide a higher pressure seal.

5. A rotary compressor according to claim 1, wherein a spring loaded valve normally closes the outlet opening for the compressed air.

6. A rotary comp-ressor according to claim 1, wherein said pivot has enlarged heads at its opposite ends, said heads having spherical external surfaces corresponding to the spherical inner surface of the housing and having a diameter greater than the inlet and outlet openings, said openings being provided at approximately diametrically opposite sides of the spherical portion of the housing, each of said hea; lng provided with an elbow-shaped canal comprising a branch opening radially and adapted to communicate alternately with said inlet and outlet openings as the shaft and vanes rotate and a second branch opening laterally into the space between the two pairs of vanes.

7. A rotary compressor according to claim 6, wherein a sealing ring is provided in a groove in each of said heads, said sealing rings circling the radial branches of said canals and being pushed out by centrifugal force against the spherical inner surface of the housing.

8. A rotary compressor according to claim 6, wherein the vanes are provided near their bases with linear grooves connected with said elbowshaped canals provided in the said heads of the pivot so that, when the facing vanes approach one another, the said grooves form passages communicating with said elbow-shaped canals, whereby residual air remaining between the vanes flows out more easily toward the outlet opening.

PIETRO PISA.

REFEREN CES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 763,963 Cobb July 5, 1904 1,376,397 Bylger May 3, 1921 2,094,143 Cady Sept. 28, 1937 2,197,959 Wentworth Apr. 23, 1940 2,482,325 Davis Sept` 20, 1949 

